1. Field of the Invention
This invention relates to the field of solid rocket engine propulsion.
More particularly, this invention relates to the actuation means to manipulate a secondary centerbody of a dual area solid propellant rocket motor having boost and sustain phase operating modes.
2. Description of the Prior Art
The prior art invention cross-referenced as a related application incorporates two discrete throat areas into one nozzle body. The foregoing is accomplished by means of the formation of a conventional throat area in a nozzle. There is additionally present, a movable plug or body which moves at the occurrence of a predetermined combustion chamber pressure drop to a sealing position with the main body wherein one flow area is presented. For example, a normal nozzle throat configuration is initially preformed. A movable flow-restriction body is disposed just upstream of the throat area of the nozzle formed. The movable body has the second nozzle area formed concentrically within itself. Thus, in an open position the hot gases flow around the movable body, through the main nozzle as well as through the movable body and its secondary nozzle. In the closed position resultant from the combustion chamber having reached a predetermined pressure drop, the movable body is flush against the walls leading to the throat area of the nozzle and the gases will only flow through the center or secondary exit. The movable body is operable by at least one piston connected to the body and disposed within a cavity surrounding the normal throat. The piston defines an upper and lower chamber, both chambers of which are in communication with the combustion chamber and sensitive to pressure changes in the main combustor. A lessening of pressure on the bottom of the piston causes the piston to translate in a rearward direction which moves the body toward a blocking position. Thus it is seen that the movable body affects the flow of gases through the first nozzle area.
The present invention does not rely on chamber pressures to actuate a centerbody into a blocking position.